The reaction of maleic diesters with certain diamines is known, as illustrated by the work of Yu. T. Tanchuk and I. A. Ral'chuk, J. Organic Chem. U.S.S.R., Vol. 14, pp. 2083-2088 (1978). In this work, the reported reaction products are a polyamide that retains the maleic acid double bond, an addition product in which each amine group of the diamine has added by Michael reaction to the double bond of a maleic diester, and a maleic diester derivative in which one of the ester groups has been replaced by an amide group (an amic ester).
Furthermore, we are aware of a prior invention disclosed and claimed in copending application U.S. Ser. No. 529,234, filed Sept. 6, 1983 in the name of Roland DiLeone, and directed to a trifunctional primary amine crosslinking agent and to a process for synthesizing the crosslinking agent. This prior proccess includes the steps of heating a reaction vessel containing an unsaturated diester of the formula ##STR1## in which R is an alkyl of 1-4 carbon atoms, and a diamine of the formula EQU NH.sub.2 (CH.sub.2).sub.n NH.sub.2
in which n=4-8, so as to remove by distillation, the alcohol reaction byproduct, and then recovering a trifunctional primary amine crosslinking agent of the formula ##STR2## in which n=4-8. The diamine/diester molar ratio is at least about 3:1. A problem with this process is the variability in yield of the desired trifunctional primary amine product of the process. In view of the usefulness this amine was found to have as a crosslinking agent for compositions based upon amine-reactive polymers, there has existed a continuing need for an improved process of making the trifunctional primary amine. Hence, the provision of such an improved process would constitute a significant advance in the art.